could I slice the PCB trace that enables autoreset and then flash using it?

Yes, that would defeat the board's auto-reset function. However you would have to re=enable the trace path for when you want to do future uploads of other sketches onto the board, or learn how to time manual resets at the proper time to allow uploads to work.

However you would have to re=enable the trace path for when you want to do future uploads of other sketches onto the board, or learn how to time manual resets at the proper time to allow uploads to work.

@Coding Badly, I have no way to update my Uno as of yet, so I plan to purchase an additional 328 for the purpose (also for a standalone project I have), which is why I need to run ArduinoISP on my current Optiboot.

@retrolefty, as the trace is designed to be cut (it's one of those bare pads) I can easily re-solder the joint to enable the functionality again.

Does Optifix update the processor on which it is running or does it update other processors?

AFAIK it's not possible to rewrite the bootloader memory internally. But if anybody wants to try out the new Optiboot v4.4 and they have two Arduino boards, the Optifix sketch avoids the need to disable auto-reset on the board acting as programmer. Once one of the boards has Optiboot v4.4 installed it will run ArduinoISP properly (again without fiddling about disabling the reset signals). Although for this purpose IMHO Optifix is easier to use than ArduinoISP + AVRdude.

It's in the last two bytes of flash memory. You can see it in the .HEX file and read it with an ISP programmer (including ArduinoISP.) To read it from a sketch, you'd need to update the protection fuses as per the source repository...

(The existing optiboot doesn't have a version number. Not even in the source code. There was only the version attached to the .ZIP file in the optiboot repository, and/or the version of the Arduino distribution. Adding the extra version number was one of the enhancements in this new version.)

I have uploaded an optiLoader4_4.zip sketch to Google Docs.OptiLoader is a superset of the earlier optifix sketch. Like optifix, it provides zero or one-button reprogramming of an Uno bootloader with the latest optiboot (4.4 in this case) while bypassing any auto-reset issues. In addition, it automatically detects chip type and will program an appropriate optiboot into ATmega168 and ATmega8 as well.

Documentation is a bit slim at the moment, but there isn't much too it. Wire as described in the ArduinoISP documentation, and run the sketch. It's designed to re-run via the reset button, to easily program multiple Arduino clones. Run a serial monitor at 19200 if you want to see what it's doing. If you put optiboot on mega8 or mega168 chips, you'll also need to have an updated boards.txt...

I've also uploaded fusebytes.zip, which pretty-prints assorted "deep" information about your Arduino. Including the optiboot version number if present and readable.

If you burned the bootloader using the existing boards.txt settings for Uno, it read-protects the bootloader from sketches, making the bootloader version number unreadable. The code changes to fix this are submitted via source, but are not part of the bootloader itself. (you COULD change the xxxx.bootloader.lock_bits from 0x0F to 0x2F in boards.txt and reburn the bootloader, but I'm not sure it's worth it.)